Croagunk(グレッグル) is the 129th Pokémon in the Sinnoh Pokédex. It is a Poison/Fighting Type, and is known as the Toxic Mouth Pokémon.

Croagunk can use one of two Abilities: Anticipation, which makes it alert to the opponent knowing either a move that is Super Effective against it or knows a One-Hit KO move; or Dry Skin, which restores HP when it gets hit by a Water-Type move or during the rain, but causes a vulnerability to Fire-Type moves and it loses HP during periods of strong sunlight. A third Ability is available to Croagunk from the Dream World, the Poison Touch Ability. This Ability affects Croagunk's moves that require physical contact, adding a 20% chance of inflicting poison

Croagunk gain the opportunity to evolve into Toxicroak starting at Level 37.

Croagunk is in the Human-Like Egg Group, and its Egg takes approximately 2,560 Steps to hatch. It takes Croagunk One Million Experience Points to reach Level 100.

Croagunk appears at the Great Marsh in Diamond, Pearl and Platinum. In Pastoria City, a Croagunk is sometimes seen walking around after the player sticks his head through the board in the center of the town, an occurrence that only occurs in Pokémon Platinum. In Heart Gold and Soul Silver, Croagunk can be found at the Safari Zone's Marshland area after placing 21 Forest Objects in the area, then waiting 20 days. Croagunk can also be found on the Rally Pokéwalker course, which can only be unlocked by way of an Event.

Croagunk appears on Route 8 during a Swarm in Black and White. In Black 2 and White 2, Croagunk can be found on Route 8, Iccirus City and the Moor of Icirrus during the Spring, Summer and Autumn months.

Croagunk appears on the School Path in Pokémon Ranger: Shadows of Almia, but it only appears once because once captured, it can become a Partner Pokémon. In Pokémon Ranger: Guardian Signs, Croagunk appears at the entrance to the Cave that's in Teakwood Forest in the Present, and in the Fire Temple missions "Which Switch Is for Mime Jr.?" and "Graveler's Terrible Rocks" by defeating it and obtaining its Slate.

Croagunk appears in the Meadow zone in PokéPark Wii: Pikachu's Adventure. First, talk to Venusaur, then battle Croagunk to obtain it. In PokéPark 2: Wonders Beyond, Croagunk can be found at Rockridge Fort in the Crag Area. Befriending it requires a disagreement to be settled, which requires both Croagunk and Scraggy to be battled, then decide which is the best battler between the two Pokémon.

Croagunk is listed in the Diamond/Pearl/Platinum, National Beginning and Melee Pokémon Scramble promo sets, the 2009 Movie Premiere Pack, Pokémon Organized Play Series 8 as a Common Card and Pokémon Organized Play Series 9 as an Uncommon Card. Croagunk is listed as a Common Card in the Mysterious Treasures, Majestic Dawn, Supreme Victors and Arceus sets.

Brock would capture a Croagunk in the episode Gymbaliar. This Croagunk would pick up where Misty and Max left off in terms of getting Brock away from females that he becomes attracted with, utilizing Poison Jab to stun Brock before dragging him away.

Throughout the Team Galactic story arcs in the Manga, Team Galactic Grunts use Croagunk as one of their Pokémon. Team Galactic Admin Saturn uses a Croagunk most often-used Pokémon along with his Abra. Additionally, Croagunk is the only Pokémon used by Looker.